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31.
GPRS无线数据传输系统的设计与应用   总被引:20,自引:0,他引:20  
利用GPRS通信技术在中低速率数据传输方面的突出优势,设计实现了一套具有高可行性和高性价比的GPRS无线数据传输系统方案.该方案具有通用性,可应用于工控、金融和交通等行业.  相似文献   
32.
提出了一种模拟高斯信源通过多中继网络进行压缩转发的系统模型,该系统模型可以描述实际中传感器受限于环境或成本,只能进行简单的模拟信号发送,而中继器能够进行复杂的分布式信源编码和信道编码的传感中继网络。本文提出了该系统的理论分析框架,对传感器网络的分布式信源编码问题,采用CEO理论建立多中继网络的率失真函数,结合Shannon信道容量理论,将传感器网络与数字通信网络建立联系。本文提出了系统的优化设计理论方法,在总功率受限条件下,在传感器网络和通信网络之间进行功率分配,使信噪比性能达到最大。理论分析和仿真结果表明,本文提出的方法比模拟中继转发系统在低信噪比区域抗干扰性能更好。在高信噪比区域,随着总信噪比约束的增大,可提高至10 dB以上。  相似文献   
33.
为了解决传统CA及其颁发的证书不能与应用紧密结合的局限性,提出一种证书模板可定制的CA解决方案。同时定义了一个通用的证书模板,用户可以通过定制证书模板来定义证书可以包含的扩展项,从而使证书带有更多关于证书持有者的信息。通过该方案,使CA能更好地面对应用,实现与应用无缝结合。  相似文献   
34.
为了解决当前高校信管专业实践教学环节存在的实践基地质量不高、实践教学内容相对陈旧、企业实习受益学生不广泛、实践教学与现实脱节等问题,通过文献研究、案例分析和归纳总结方法,文章提出了实践教学模式变革的方向,即建立"五位一体"的信管专业创新创业实践教学和管理体系.该体系包括"健全的组织管理体系、创新创业人才培养模式、创业支...  相似文献   
35.
针对目前电子行业中许多中小型企业、高校或个人有对电路板进行小批量贴片的需求,以及市场上缺少工业化实用性设备的问题,该文提出了一种小型化低成本的桌面型贴片机。首先为桌面型贴片机设计了一种紧凑型结构,完成了视觉系统的选型;然后提出一种上视相机的专用标定方案;最后提出并完成了基于几何外形特征的芯片校准方案,为后续紧凑型桌面贴片机的工业化和成熟化奠定基础。  相似文献   
36.
林舒琪  陈瑞丹 《中国园林》2022,38(4):110-114
从圆明园盛期的施工文件《圆明园内工则例》入手,探讨其盛期的植物种类,以期为圆明园的修复展示工作和皇家园林植物配置研究提供参考。对《圆明园内工则列》中的《花果树木价值清单》定种中有争议和模糊定种的植物如刺松、马英花、槟子、沙果、探春花、黄海棠、欧栗子,以及笔者提出异议的罗汉松、红白丁香、白樱桃进行了详细考据和论证定种。  相似文献   
37.
Photodegradation of plasticized poly(vinyl chloride) (PVC) stabilized by different thermal stabilizers including organic calcium complex and mercaptide organotin was investigated. Plasticized PVC sheets prepared by an open twin‐roller mill and plate vulcanizing machine were exposed to xenon‐arc light with the irradiance of 0.51 W/(m2·nm) at 65°C. A much better color stability displayed by mercaptide organotin than organic calcium complex has been confirmed by digital photos and color difference. This can be explained that the more effective mercaptide organotin minimizes the amount of thermal damage from processing thus favours subsequent UV weathering. Carbonyl index and decomposition activation energy (Ea1) obtained from attenuated total refection‐Fourier transform infrared spectra (ATR‐FTIR) and thermogravimetric (TG) analysis, respectively, further indicate that plasticized PVC sheets containing mercaptide organotin have more excellent UV resistance. Mechanical tests reveal that photodegradation of PVC is accompanied by the predominant process of chain scission on the surface of samples. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.  相似文献   
38.
The effect of the combination of a benzotriazole type of UV absorber (UV326) with different types of thermal stabilizers, including an organic calcium complex and an organotin mercaptide, on the photodegradation of poly(vinyl chloride) (PVC) was investigated by color difference measurements, UV‐vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and viscosity‐average molecular weight (Mη) determinations. Films of PVC containing 0.5 phr of UV326, with or without 2 phr of thermal stabilizer, were prepared by solution casting and subjected to accelerated UV weathering under xenon light with an irradiance of 0.51 W/(m2 nm) at 65°C. The results revealed that both UV326 and the mixture of UV326 with the organic calcium complex displayed good performance in inhibiting the photodehydrochlorination and photooxidation of PVC. In contrast, the combination of UV326 and the methyltin mercaptide remarkably accelerated the discoloration of PVC when the irradiation time increased from 300 to 400 h because of the UV sensitivity of the organotin. However, carbonyl index data indicated that a hydrogen abstraction reaction did not take place between UV326 and the methyltin mercaptide, so that the photooxidation of the PVC film was prevented effectively during the whole period of exposure, a result which may be attributed to the strong steric hindrance effect of the tert‐butyl group at the 3‐position of the phenyl ring in UV326. The changes of Mη were in good accordance with the results obtained from other characterizations. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers  相似文献   
39.
Zhang  Kunlin  Xu  Jihui  Xu  Huaiyu  Su  Ruidan 《Multimedia Tools and Applications》2020,79(23-24):16663-16681

Axle is an important part of high-speed train. The axle is the key component connecting the train wheelset, which has a great impact on the train safety. The health monitoring of axles is very important for the safe and smooth operation of trains. The axle health detection is a complex process of multi-factor coupling, which faces the problems of health model construction. From the perspective of big data visual analysis, this paper helps people find the information behind the big data of high-speed railway axle monitoring, and makes a prediction and analysis of the health status of high-speed railway axle operation. Starting from the present situation of scatter plot presentation of multi-dimensional data visual analysis, this paper proposes a visual analysis and processing method for high-speed train axle health monitoring, aiming at the problems of intensive rendering, visual mutation and trend prediction when drawing large data scatter plot. Firstly, a new method of the axle data fusion model is proposed in this paper, which can effectively clean the axle health monitoring data and construct the data acquisition and expression mode of axle temperature of high-speed train. Then, visualization of axle data and prediction of axle health trend provide a new analysis model for axle health monitoring. In addition, the visual analysis method of scatter density map data can eliminate the dependence of the original complex mechanical model, and can be used to analyze different working conditions and axle types. Compared with the existing axle health monitoring methods, this method has high accuracy and practicability.

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40.
使用已设计实现的高性能密码服务器系统[2]作为TSS系统底层密码功能的硬件实现,给出了TSS系统的分析与设计。通过使用多线程技术,使TSS可以充分调度密码服务器中密码模块上的多个密码芯片的运算功能,从而支持并行产生时间戳签名操作。为了降低因频繁产生和频繁释放服务器工作线程所引起的系统开销,设计了工作任务线程池用于产生和管理TSS的服务工作线程,并给出了线程池维护管理算法的设计与实现。  相似文献   
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